A muscle spasm is a sudden, involuntary movement of one or more muscles.

A spasm is described as an involuntary muscle contraction, when measured by electomyography, or as spontaneous motor unit activity (Travel, Simons, 1983).

  • Muscular defense is a reflex which is a muscular spasm in response to pain.
  • This painful stimulus is due to local tissue damage and is present in the acute phases of a condition.
  • Muscle spasm acts as a functional protection of injured structures, reducing movement and preventing further injury.
  • Muscular defense can also result from referred pain.
  • In both cases, the muscular defense disappears when the pain is relieved (Kisner; Colby, 1990; Janda, 1991).
  • However, the idea that muscle spasms protect injured tissue has led to the overuse of immobilization, such as bed rest or splints to treat spasms, especially those associated with trauma.
The pain-spasm cycle.
  1. Pain resulting from direct or indirect trauma, inflammation or infection can trigger a muscle defense contraction.
  2. Increased excitation of the sympathetic nervous system, emotional stresses, cold or cooling of tissues and immobilization also lead to muscle defense contraction.
  3. This contraction restricts joint movement.
  4. Lack of movement causes tissue ischemia or circulatory stasis and retention of metabolites, which in turn irritate nerve endings, resulting in pain.
  5. The muscle responds to pain by remaining in spasm.

This spasm will remain even when the tissue damage that caused the initial muscular defense reflex is no longer acute (Kisner; Colby, 1990; Cailliet, 1993; Rachlin, 1994).

Muscles that frequently spasm

  • Gastrocnemians
  • Soleus
  • Hamstrings
  • Quadratus lumborum
  • Intrinsic back muscles
  • Intercostals
  • Sternocleidomastoid.

Causes of muscle spasms and cramps include:

â–º Pain resulting from inflammation, direct or indirect trauma or infection;

  • Circulatory stasis due to reflex muscle defense, restriction of movement and decreased circulation
  • Increase in gamma neurons due to stress, anxiety, fatigue, or injury from overstretching nearby tissues.
  • Cooling of the muscle resulting in a contraction of reflex muscle defense;
  • Nutritional alteration.
    • Decreased calcium intake
    • Sodium loss
      • Excessive sweating
      • Dehydration
      • Electrolyte disturbance due to persistent vomiting
      • Hypocalcemia due to persistent diarrhea
  • Lack of vitamin D, because this vitamin helps to synthesize enzymes that actively transport calcium, necessary for normal muscle contraction (Dunne, 1990).
  • Trauma
  • Muscle overuse
  • Emotional stress
  • Cold muscles
  • Prolonged immobilization,
  • Ischemia (temporary lack of oxygen in a localized tissue)
  • Dehydration

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